Not Everything Is Physical
For most people it is obvious that not everything is physical. Unfortunately, the reason for that belief is very often not based on reason, but superstition, including mystical beliefs in spirits, the supernatural, and the incorporeal.
Nevertheless there a many perfectly natural things that exist that are not physical and knowing them requires no mysticism.
What Is Physical
The physical is all that exists that can be directly perceived, that is, seen, heard, felt, smelled, or tasted, including all that can be discovered or learned about the perceived using instruments and reason.
All that can be known about the physical is in terms of physical attributes or qualities, those that can be directly perceived like color, sound, texture, smell and taste, as well as all the discovered properties of the physical such as weight, shape and temperature, as well as, chemical properties, and biological properties.
Ideas and Language
Do you have any ideas? If you do, what color are they, what kind of sound do they make, what do they feel like, smell like, or taste like? How heavy are your ideas, what shape do they have, and what is their temperature? What are their chemical properties or biological properties? These are all physical attributes that all physical things have at least some of. They are what makes physical things physical. Whatever does not have these properties is not physical.
Ideas do not have any physical qualities or attributes. Even when recorded, written in books or recorded digitally, while the paper and marks on it, and the electrical states of digital memory are physical, the ideas themselves are not physical and do not exist in any recording device.
The same idea may be described in any language, and it is the same idea no matter what language it is written in, because it is not the marks on a piece of paper that are the idea, but the meaning the writer intended and the reader understands that is the idea. Ideas have no physical attributes and do not exist physically, ideas only exist in human consciousness.
No knowledge or knowledge method exists physically. Language, mathematics, geometry, logic, all the sciences, history, literature and human invention only exist intellectually in human minds.
You Can't Eat Ideas
One of the many recent popular ideas infecting society with irrational fears was expressed to me as follows, "I don't want any chemicals in my food." My question to this fool was, "what do you propose to eat? Poems?"
The entire physical existence is chemicals. Human beings are chemicals and all their food is chemicals. If ideas were physical, they would be chemicals too, and perhaps we could eat them. They would be easier to produce then what we currently eat.
I know the entire world of sub-atomic physics is not chemicals, but, oddly enough, sub-atomic existence is contingent on chemical existence. The physical is that which is known by the direct perception of it. Everything else, including the physical sciences must be deduced from that. If there were no directly perceived physical (chemical) existence there would be nothing for the sciences to study or chemistry to explain.
Do trolls, angels, and magic dragons exist? They certainly do not exist physically, but they do exist as ideas, fictional ideas invented by human beings. Not everything that exists if physical.
[NOTE: See the articles: "The Nature Of Life," "The Nature Of Consciousness," and "The Nature Of Mind," which describe the non-physical nature of those attributes of organisms, and "Physicalist Superstition," which explains what is wrong with the view there is only the physical.]